Method for pouring concrete structures



Feb. 17, 1959 A. SHELDON METHOD FOR POURING CONCRETE STRUCTURES 2Sheets-Sheet 1 Filed Nov. 26, 1954 a ATTORN Y INVENTOR k/vozo Aka-200wFeb. 17, 1959 A. SHELDON METHOD FOR POURING CONCRETE STRUCTURES 2Sheets-Sheet 2 Filed Nov. 26, 1954 ATTORNE United States PatentO METHODFOR POURING CONCRETE STRUCTURES a Arnold Sheldon, Glen Gardner, N. J.Application November 26, 1954, Serial No. 471,380

1 Claim. (Cl. 25-155) The present invention relates to a method forpouring concrete structures.

The invention is described as embodied in flexible forms for pouringconcrete walls of various kinds having curves of various radii andtangents to the curves and in methods of making various structures, forexample, such as swimming poolshaving vertical or inclined serpentinewalls.

Among the advantages of the method of pouring concrete walls. describedis that it enables a completely formed floor, wall, and cap to be madein three pouring operations. Or, where the top of the wall is formedwithout an overhanging cap, a complete footing and wall can be made withtwo pouring operations.

every case is a precision cast wall. And even for very large walls themethod can be performed with only two The result in the methoddescribed, two men are enabled to build a-l are those resulting from thefact that they are simple, strong, and rugged and very easy to use,lending themselves readily to use by the average homeowner.

The forms are very easy to fabricate and consequently are these formscan be used over and over again, for many years, their cost per jobbecomes insignificant. The forms described have concrete supportingfaces of smooth flexible sheet material, sheet steel being used in theparticular forms described. The particular forms described,withcomparatively low in initial cost, and, moreover, because outmodification or adaptation, can be used to build a wall of any lengthand thickness and of any curvature or combination of curves with aradius of 5 feet or larger.

Sharper bends can be formed by the use of thinner gage sheet material inthe forms.

In forming walls opposed sets of flexible sheet forms are used, one setof the forms being bolted to anchors in a previously cast footing(orfloor), and the other firmly held in uniformly spacedrelationshipfrom the first set and advantageously being supported and,in some in- For example, in building a pool, the outer forms for thepool wall may be "bolted to the perimeter of the floor with the innerforms stances, suspended from the first set.

coupled to the outer forms and supported from them.

The forms described have smooth faces and are well suited for the use ofvibration devices during the pouring.

With these forms the highest quality of poured concrete can be obtained.

The forms described include rows of perforations running parallel to thetop and bottom edges of the form.

Where desired, vertical stiflening elements may be secured to the outersurface of the sheets in the forms, either permanently or temporarily.For very gradual curves or straight tangents additional longitudinalstiffening elemerits may be used with the forms.

' the forms in one or two jobs.

ice

In casting a serpentine wall as described, a number of flexible forms inend-to-end relationship isarranged to define the desired curves. Thesefirst forms assume the desired wall curves because they are bolteddirectly, or indirectly, to a previously cast footing (or floor). Thesefirst forms have two rows of closely spaced perforations runningparallel to and near the top and bottom edges of the sheet,respectively. A second group of similar forms with at least two rows ofholes parallel to and near the top and bottom edges of the sheet areused to definethe other face of the wall. The second formsare spaced atuniform distance from and supported fromthe first forms by means ofconcrete form ties and lag bolts. The holes in the second forms beingspaced at distances corresponding'to the desired spacing of the ties.

Because of the close spacing of the holes in the first forms, one ofthese holes is always substantially opposite a hole in the second formsand thus, regardless of the curving of the forms, it is easy to runconcrete form ties between opposite pairs ,ofholes and thus to obtainthe desired uniform spacing of the forms. t

Advantageously, when the second forms are removed from the exposed faceof one side of the wall, it is found to be as smooth as the surface ofthe steel sheet material of the forms and requires no further finishing.I have found that there is substantially no leakage of cement from therows of closely spaced holes in the first forms, even though most ofthese holes are left open when the forms are set up and the concrete ispoured. The rows of small bumps which are formed being readily smoothedoff or being covered by earth. For example, inmaking a swimming pool,the first forms with the closely spaced holes are arranged around theoutside of the pool. Advantageously, the serpentine wall obtains greatlyincreased rigidity and resistance to overturning due to its curves. Ineffect, the concrete is in horizontal arches, and therefore,advantageously is in compression when lateral forces are applied.

Among the many advantages of the curved wall construction described, forexample, in the case of building walls or retaining walls, is the factthat the walls have greatly increased strength both due to the archeffect, which iswell suited to withstand side loads such as are exertedby an embankment or by theearth around a swimming pool in pressing itagainst the wallsfof the pool, and due to the corrugation eifect inproducing a better vertical load "bearing wall. The convex portions ofthe curves act in effect as abutments extending, out from the averageposition of the centerline of the wall. The result is a great increasein the strength of the concrete. Because of the strength inherent in thedesign, a minimum percentage of reinforcement is needed; the resultantsaving in cost, in many instances, pays for the initial cost of Theserpentine concrete wall described herein is capable of sustainingunusually large loads, both in compression from top to bottom andbending and overturning forces, such as those experienced by the wall ofan empty swimming pool when the earth is saturated with rain, or duringfrost. heaves. These large forces would simply buckle in'a flat wallcontaining the same amount of concrete. t

The curved walls described can be made thinner, resulting in a furthersaving in material, this also saves in the overall weight of thestructure and in the required size of the foundations, thus enabling atwo-fold saving, in addition to the saving in reinforcement discussedabove. i t

In building a swimming pool with inclined walls,in accordancewith themethod described, low flexible forms are used in casting a curbingaround the excavation at its lip. The inner form is then suspended bymeans of cantilevered form ties from the curbing and from the of Figure1;

top of the inner form. When the concrete is poured between the curbingand the suspended form, the concrete runs down the sloping wall of theexcavation and into the bottom to form the sides and bottom of the poolwhich may then be troweled up to smooth any rough places, completing thepool. When the method of the present invention is used in buildingretaining walls, the wall is made serpentine so that it alternatelycurves toward and away from the 'embankment which it is supporting. Thefootings for the wall are cast so that they all project into theembankment asfar as the nodes of the curves. The result is, in efiect,to. provide cantilevered arms projecting inwardly from the outwardlycurving portions of the wall underneath a substantial portion of theembankment so as to resist any overturning forces exerted by theembankment against the retaining wall. The resulting structure isextremely strong and requires only a fraction of the "amount of concreterequired in the usual type of battered wall used to retain embankmentstoday.

.The forms described lend themselves most readily to the building of awide variety of different footing and wall arrangements, including wallswith walking strips adjacent the bottom or top of the walls. The methoddescribed is well suited for building terraced garden arrangements, orscalloped wall bay arrangements, and is highly advantageous in buildingtanks.

The various aspects and advantages of the present invention will be morefully understood from the follow- I ing description considered inconjunction with the accompanying drawings, in which:

Figure 1 is a partial perspective view, partially in section, of aconcrete swimming pool made with the method and apparatus describedherein;

Figure 2 illustrates the first step in the building of the swimming poolshown in Figure 1; I

Figure 3 shows the inner and outer wall forms in place ready for thepouring of the wall of the swimming pool Figure 4 shows the forms inplace for the pouring of v the coping, which completes the swimmingpool;

Figure 5 is an exploded perspective view of the first and secondflexible forms used in supporting the outside and inside surfaces,respectively, of the pool shown;

Figure 6 is a partial perspective view of the flexible form used forcasting the coping along the top of the wall of the pool;

Figure 7 is a partial perspective view ofv the flexible form used inmaking walkways adjacent the tops or bottoms of walls;

Figure 8 illustrates a method of pouring curved sloping pool walls;

v Figure 9 illustrates the way in which abutting edges of the form aredisengageably locked together; and

Figure 10 shows a wall tie with a cradle secured thereto for supportingand aligning horizontal reinforcing rods.

As shown in Figure '1, the swimming pool includes a I generallysaucer-shaped concrete bottom 10 which curves upwardly around the edges,which edges may be somewhat thicker than the center so as to form afooting portion 12 beneath the wall 14. Because of the inverted archshape of the bottom 10, the concrete therein is in compression and thusrequires only a minimum of reinforcing material as may be required forresisting stresses due to temperature variations. The bottom It mayinclude spaced reinforcing rods but usually a layer of 6 inch squarereinforcing wire mesh 15 is sufficient. lengths of rods 16 spaced everyfew feet are driven into the earth and left standing so as to beincluded in the footing portion 12 with their ends projecting above thetop surface 17 of the footing 12 to provide a good bond at theconstruction joint with the wall 14 which is poured after the integralbottom and footing ,have set.

Also, the surface 17 is trowelled rough as it hardens to provide betterbonding with the wall 14.

Short Also, a key-way may be formed by laying a plast pipe temporarilyalong the surface 17, the pipe being removed before the wall is pouredto have a semi-circular recess extending along the length of the footing12.

' The wall 14 is serpentine, of uniform thickness, and vertical. Aswimming pool with a sloping serpentine wall is described later. Thewall 14 may include vertical reinforcing rods 18 spaced along the wall,with the upper ends 20 of these rods 18 projecting above the roughenedtop surface 21 of the wall 14, so as to provide a good constructionjoint with a coping portion 22 which may be cast on top of" the wall 14.When the coping 22 is included, the rods 18 are bent outwardly at rightangles to the wall 14, as indicated by the dotted arrow, before thecoping is poured, to reinforce this coping, which has a generallyinverted L-shape, as seen in cross section. The coping 22 is pouredafter the wall The coping may include a number of longitudinalreinforcing rods 24; for example, four rods are shown runninglongitudinally along the length of the coping. Three of these rods 24are spaced at uniform distances beneath the upper surface of the coping22 and the fourth rod is in the lower portion of the coping 22 whichoverhangs and projects down along the outer surface of the wall 14.Among the advantages of these forms are their smooth, obstruction-freeupper edges which act as guides to facilitate screeding off. These edgesmay advantageously be used as tracks on which to run a small Weightedtruck 25 described in detail later.

Instead of using a coping, the reinforcing rods 18 may be ended belowthe top surface 20 of the wall and this surface then screeded off smoothon a level with the top of the outer form to finish the pool, asexplained in detail below.

Figures 2, 3, and 4 illustrate a method embodying the present invention.Some of the various reinforcement elements shown in Figure l are omittedfrom Figures 2, 3, and 4 in order to make the various steps of themethod more clear, but it will be understood that reinforcing rods andwire mesh are used as described above and would be bent at the varioussteps in the building of the structure, as explained in connection withFigure 1.

In order to cast the bottom 10 ofthe pool, a low flexible form 30,- asshown in Figures 2 and 6, is staked in position in an excavation bymeans of iron stakes 32. Each stage projects down through the bight of aU-shaped bracket 36 somewhat above mid-way between the upper and loweredges of the form 30. The stakes 32 are releasably locked to thesebrackets 36 by metal wedges 33 driven horizontally through transverseholes in these brackets. The inner surface of the form 30 is used to todefine the outside face 40 of the footing portion 12.

Each of the forms 30 is of No. 10 gage steel sheet 12 inches high and 8feet long. As shown in Figure 6, an upper and lower row of holes 41 and42, respectively, are provided extending, respectively, along parallelto and 3 inches down from the top and 3 inches up from the bottom edgesof the form 30. These holes are hi of an inch in diameter 1 inch aparton centers, and extend the full length of the form 30. The features ofthe connection means used at the ends of these forms 30 are discussedlater. The forms are connected in abutting relation to form a smoothcontinuous inner surface. Through the lower row of holes 42 are insertedlag bolts 43 which fit snugly and are screwed into concrete bolt anchors44 so as to support the anchors, which are then cast into the concrete,for purposes described hereinafter. These anchors 44 comprise ahelically formed wire with spaced turns, the turns being welded to apair of diametrically opposed rods extending longitudinally of thehelix. Such anchors are available commercially from Superior ConcreteAccessories Corporation as Cone-Fast Coil Ties, or from the DaytonCompany as RichmondTies. As many as four bolts 43 opposite thecorresponding rows in form 48. "lag bolts 56 are then inserted throughthe holes 54 in and anchors 44may be used for each form 30, spacedevenly along itslength, but usually two bolts and anchors are entirely.adequate.

With these anchors 44, I use spreader cones 46 around the shank of eachlag bolt adjacent the surface of the concrete so that after the concretehas set and the lag bolts are unscrewed, these cones 46 can be removedleaving funnel-shaped openings to provide easy access to the anchors 44,which are used in the next step of the process. Moreover, the resultingfunnel-shaped openings in the concrete are easy to point up, after thewall is complete, and leave the anchors 44 spaced a distance in from thesurface of the concrete in accordance with good practice.

The outside portion of the rough top 17 of the footing comes up to alevel about one inch below the bottoms of the upper holes 41. When thebottom and footing 12 have hardened, the flexible forms are removed byremoving the wedges 38, pulling up the stakes 32, and unscrewing the lagbolts 43.

As shown in Figure 3, the next step is the bolting in place of theoutside flexible wall forms generally indicated at 48 against theoutside face of the footing 12. The form 48 (see also Figure 5) is also10 gage sheet steel. It is 3 feet high and 8 feet long. It includesthree I rows 50, 52, and 54 of closely spaced holes. The upper row ofholes extends along three inches from the top edge of the form 48, andthe second row 52 extends along nine inches above the bottom edge of theform 48. The third row 54 is three inches above the bottom edge. Theseholes are all 3 of an inch in diameter and spaced on one inch centers.

Because the holes in the lower row 54.are so closely spaced, fourofthese holes in each form 48' line up with the four funnel-mouthed holesand anchors 44 left when the four lagbolts 43 and cones 46 were removedfrom each of the forms 30. This alignment of the holes in row 54 and ofthe anchors 44 occurs regardless of the curvature of serpentine .form ofthe face 40 of the footing 12, and because the holes in row 54 are M ofan cally outside of each form. These studs are 3 .feet

high, each with three holes 50', 52, and 54' positioned Longer the studs55 and through whichever holes in .the row 54 are aligned with theanchors 44, and are tightened;

firmly to hold the forms 48 to the footing.

In order to secure the inner flexible forms 58 (see also Figure 5) inplace, the upper and intermediate rows 50 and 52 of holes in the outerforms 48 are used. The

forms 58 include three rows of 4 inch holes spaced tom edge of the form58 is rested down on the inneri. .edge of the footing 12 with the bottomrow 64 opposite theintermediate row 52 of the form 48. The intermediaterow 62 is opposite the top row 50. Four studs 65 may be used with theinner forms 58; These studs are identical with the studs 55 except thatthe two holes 60 and 62 are at the top to correspond with the rows60 and62.

Because of the close spacing of the holes in the rows 50 and 52, one oranother of these holes is always located opposite to a correspondinghole in the interme-.

* diate and bottom rows 62 and 64 of the inner form 58, regardless ofthe curvature being used. However, with 'No. 10 gage steel, I find itpreferable to keep all curves at least 5 feet in radius. Where sharperbends are desired, thinner gage steel. is used. Ifind that the. thinner'6 gage forms are entirely satisfactory for supporting concrete withsharper bends because these sharper bends provide a stifiening action,as explained above, which offsets the greater flexibility terial.

Where very gradual bends are being made, I find that it is sometimesdesirable, as described in detail later, to provide additionallongitudinal stiffening for the forms 48 and 58 by using one inch thickroofing boards between the outer surfaces of the forms and the studs 55and 65, respectively.

Suitable lengths of form coil ties 68 are inserted between the two forms48 and 58 and more lag bolts 56 are screwedthrough the holes in thestuds 55 and through the aligned holes in forms and into the oppositeends of the form ties 68. These ties 68 are similar to the anchors 44except that two helically wound wires are used at opposite ends toprovide threads for engaging the lag bolts 56, and the rods in the tiesare of a length to span between the spaced forms. These rods arepreferably arranged one above the other to provide a slight degree oflateral compliance to aid in inserting the lag bolts. The ties 68 arecast. into the concrete. Cones 46 are also used with them, as 'shown.The forms .48 and 58 are uniformly spaced.

,In order to secure the ends of the form 48 and 58 in abuttingrelationship with the ends of the respective adjacent forms, as shown inFigure 9, by 2 inch angle of the thinner gage ma- .irons, 2 feet longare welded along parallel to the ends of all of these forms with thelonger lag outstanding. In order to interlock the forms, againstrelative lateral shifting, I find it desirable to have the angle ironsat one end of each form spaced back a slight distance from the edge sothat the projecting edge forms a lip 73, for

example, as shown in, Figures 6 and 8. At the opposite end the angleiron projects beyond the edge of the form to leave a rabbeted socket forreceiving the lip 73. These angle irons leave 6 inches at the top andbottom edges of the forms free for the use of longitudinal stifieningboards, as discussed below. Three inch holes are provided in each angleiron for the use of slotted key bolts 72 and wedges 74, as indicated inFigure 9, to. lock the forms together.

The next step is the pouring of the concrete between the forms 48 and 58to form wall 14, as indicated by the arrows in Figure 3. The top 76 ofthe wall 14 is made rough and on a level with the top of the form 48,leaving the top edge of the inner form projecting 6 inches above the top76. The upper row of holes 60 in the inner form are used in theconstruction of the coping, as explained later.

As soon as the wall 14 has set, the outerform 48 is removed byunscrewing the lag bolts. At this point the wall is backfilled up to alevel 77 about six inches'below the rough top surface 76. In place ofthe lag bolts which were .in the outer ends of the upper ties 68, studbolts 78 are inserted. These stud bolts are then used to supportadditional form ties 79 (see Figure 4) which are cantilevered out fromthe stud bolts and connected by short lag bolts 43 to the lower row 42of holes in the same flexible narrow form 30 which was used for formingthe floor and footing. The top row 41 is aligned with correspondingholes in the top row 60 of the inner form 58, and the forms 58 and 30are then fastened together by short lag bolts .43 and double length coilties 88, as shown in Figure 4. The ends of these forms 30 are fastenedtogether by by 2 inch angle irons (see Figure 6) using slotted key boltssimilar to those shown in Figure 8. These angle irons are arranged toprovide a lip 73 for engagement with a rabbeted socket similar to thatdescribed in connection with forms 48 and 58. The bottom edge of the legof the angle irons 90 are cut off at an angle and thetop of the angleiron is spaced down from the top edgeof the form 30, as shown, toprovide. clearance for longitudinal stiffening elements,

where desired. The coping 22 is then cast in place between the top edgeof the inner form and the form 30, resting down on the top 76 of thewall and on the backfilled earth 77. As soon as the coping is dry, theform 30 and the inner wall form 58 are removed, leaving a completedswimming pool.

When it is desired to make the wall 14 without a coping or cap 22,shorter reinforcing rods are used and its top 76 is screeded oil levelwith the top edge of the outer form 48 at the completion of the stepshown in Figure 3. If desired, the wall can be made 6 inches higher byclamping the lower edge of the outer form against the top of the face 40using clamping pieces held by bolts in the anchors 44 in the footing.Then the top edges of the inner and outer forms 48 and 58 are at thesame height and can be used to guide a weighted screeding truck.

Figure 4, the reinforcing rods 24 are wired to the underside of thedouble length ties 88 and the lower rod 24 to the tie 79.

In order to minimize the number of forms required to complete largersize swimming pools, I have found it advantageous to cast the entirebottom 10 at once.

- Then I cast one half of the wall 14, and then use the same forms tocast the opposite half. I may use the coping 22 as a means of furthertying the two halves of the wall 14 together. This tying action isobtained by stopping the ends of the first half of the coping somewhatshort, for instance three or four feet short, of the ends ofthe firsthalf of the wall. Then, the second half of the coping overlaps three orfour feet of both ends of the first half of the wall so that the twoparts of the wall are firmly united by the overlapped coping.

In order to provide longitudinal stiffening for the forms 48 and 58 whenthey are used to build straight walls or walls having a slightcurvature, I may stiffen the upper and lower edges of the forms by 12 or16 foot stringers of ripped pine roofers one inch thick and about 2 /2inches wide placed immediately above and below the lag bolts through thetop and bottom rows of holes in the wall forms. The joints-in thesestringers are staggered from each other and from the joints in theforms. In addition, where desired, one by six inch roofing boards 7%feet long may be placed against the outer surfaces of the forms 48 and58.

A highly advantageous method for pouring a sloping retaining wall, forexample, for making a swimming pool, is illustrated in Figure 8. Anexcavation is made and the walls of the excavation are pushed out andback by a bulldozer to form sloping earth banks 92. A curbing 94 is thencast around the upper edge of the banks with its inner face at the lipof the bank. The outer forms used for the curbing 94 are the forms 30.The inner forms 96 are similar to the forms 30 but have only four holesin each row 41' and 42 spaced on 2 foot centers. The forms 30 and 96 areremoved after the curb has set. The level of the top of the curb isspaced about mid-way between the rows of holes 41 and 42 in the forms 30so that one row of coil ties 68 is cast crosswise through the curbing94. Stud bolts 78 are inserted into the inner'ends of the coil ties 68in curb 94, and other coil ties are then used to cantilever the forms 96in position inside of the inner face of the curb a distancecorresponding to the desired thickness of the walls 98 of the pool,indicated in phantom. The top rows of holes 41 are connected by longercoil ties 88 to the holes 41, as shown, so that .reinfor'cing rods100dri-ven in the ground and left standing are cast vertically in thecurb and then bent over and down into the center of the wall. Concreteis then poured between the forms 30 and 96 and is allowed to run downthe bank 92. A man in the excavation in hip boots trowels up the innersurface of the walls 98. The bottom of a pool with sloping walls 98 maybe of poured concrete or may be an impervious dirt layer.

So far only two sizes of forms have been described: these include forms30 and 48, which have rows of closely spaced holes and theircorresponding opposed forms 96 and 58, respectively, which have rows ofholes spaced on 2 foot centers. These forms can be used to make wallswith or without caps and of variable radii, as already described. Also,using forms 48 and 58, walls of any height can be made, as will beapparent from Figure 3. After the wall 14 has set, the forms 48 and 58are unbolted, raised up and have their lower rows of holes 54 and 64bolted to the upper anchors 68. This process is repeated as many timesas desired. A coping can be formed at the wall top, if desired.

A third size of form 102, as shown in Figure 7, can be used to, obtaineven a wider variety of walls, footings, and walkways can be built. Thisfoim is 6 inches high and 8 feet long with a row of holes on 2 footcenters down the middle, and with stake pockets 36 similar to those onforms 30. When these are staked to the ground adjacent the top or bottomof a wall, a sidewalk can be readily formed. For example, in place ofthe form 30 in Figure 4 a form 102 is staked along the top 77 of thebackfill, which in this case would be level with the surface 76, at adistance from and parallel to the upstanding edge of the inner form 76,to make a walkway around the outside of the top of the wall.

By using the forms 102 spaced in from the lower edge of the forms 58, awalkway or horizontal shelf for swimmers to stand on is formed aroundthe floor of the pool adjacent the wall 14.

Along the unobstructed top edges of the form may advantageously be run atruck, as indicated at 104 in Figure 4. Such a truck may be used to dumpor spread the concrete mix, but as illustrated here is a small weightedtruck fitted with flanged wheels 106 to run on the form edges. The truckcarries a small electric vibrator 108 of the external form type to givelateral side to side vibration. Across the front of the truck is ascreed 110 angled so as to plow oif any excess mix and dump it to theoutside of the forms. The wheel flanges are spaced to accommodate slightirregularities in the forms.

These flexible forms are highly suited for the use of internalvibrators, for the forms are so unobstructed. Also, external vibratorscan be applied to their outside faces, shaking the concrete downsmoothlyand densely against the opposed concrete-supporting faces of the formsto yield the highest quality of poured concrete with smooth attractivesurfaces.

With these forms, a somewhat drier concrete mix can be used,advantageously increasing the strength of the structure.

I have found that only an insignificant amount of concrete tends todribble out of the pluralities of open holes in the various rows,described above. The resulting bumps on the outer surface of the wallsare easily smoothed oif after the forms are removed.

Where drier mixes are used, substantially no concrete comes out throughthe V inch holes.

Where curves of shorter radii are formed, the abutting edges of theinner sheets may tend to meet at an angle. I pull these edges into asmooth curve by using coil ties and cones against theconcrete-supporting faces of the forms at their joint. A lag bolt passesout from the coil tie through aligned notches in the abutting form edgesand through a hole at the center of a 2 by 3 board which is about a footand a half long. Tightening up the bolt pulls the abutting edges into asmooth curve.

Although the forms have been described as inner 9 and outer forms, theirrelative positions can be reversed by casting the footing with anupstanding rim to provide a face such as the face 40 of Figure 2, butfacing inwardly.

In order to locate and hold reinforcing rods in position, whenever theymay be used, the various wall ties may advantageously have chairs orcradles secured thereto. For example, as shown in Figure 3, a U-shapedchair 112 is welded to the lower cross tie 68. This chair 112 is formedby a stilf wire or thin rod bent into a U-shape with its legs straddlingthe tie and projecting up on either side. The legs of the chair are thuslaterally and longitudinally offset so as also to be able to straddleand hold a reinforcing rod 114, which in some instances may be included,extending lengthwise in the bottom portion of the wall 14.

In Figure is shown a dual cradle 116 for supporting two horizontal rods118 in side by side relationship. The cradle 116 is formed of a stiffwire or thin rod bent into a generally bridge-truss shape with twopockets 120 at the top near either end for supporting the rods. Thelower ends of the two legs 122 of the cradle are welded to the cross tie68" near either end. The tie 68' is similar to the tie '68 but islonger, for forming thicker walls.

A further advantage of these forms is that when the ties are secured inplace they help to hold the curvature of the forms in the horizontalplane, and the horizontal curvature holds the forms vertically straight.

From the foregoing description it will be understood that I haveprovided a method well adapted to yield the many advantages describedabove. It will be understood that the forms of the present invention aresubject to modification and changes as may best fit them for eachparticular application, and that the scope of the present invention isintended to include such modifications or adaptations, as defined by thefollowing claim, limited only by the prior art.

The subject matter divided from this application is 10 claimed in acopending application Serial No. 686,813, filed September 25, 1957.

What I claim is:

The method of casting a curved concrete wall comprising the steps ofcasting a footing having at least one vertical face defining the desiredcurvature of one surface of the completed wall, securing a flexiblesheet against said face to conform to the curvature of said face,curving a second flexible sheet to conform to said first sheet andsecuring said second flexible sheet to said first sheet at a firstuniform distance from said first sheet, casting a wall portiontherebetween on top of said footing, removing said first sheet,supporting a third flexible sheet at a second greater uniform distancefrom said second sheet than was said first sheet backfilling adjacentsaid third sheet, and casting a top portion of said wall between the topof said second sheet and said third sheet.

References Cited in the file of this patent UNITED STATES PATENTS811,032 Byor Ian. 30, 1906 1,044,862 Crary Nov. 19, 1912 1,141,057Heltzel May 25, 1915 1,446,681 Wire Feb. 27, 1923 1,517,244 Martin Dec.2, 1924 1,628,316 Heltzel May 10, 1927 1,922,584 Heltzel Aug. 15, 19332,523,131 Martin Sept. 17, 1950 2,506,485 Boudousquie May 2, 19502,614,311 Shook Oct. 21, 1952 2,669,000 Seeman Feb. 16, 1954 OTHERREFERENCES Engineering News-Record (1), Feb. 2,. 1950.

Engineering News-Record (2), Mar. 2, 1950. Engineering News-Record (3),Apr. 20, 1950.

